1. Field of the Invention
This invention relates to a process for the production of aqueous solutions of alkali metal, alkaline earth metal, ammonium and/or amine salts of sulfonated fatty acid glycerides by sulfonation of unsaturated fatty acid glycerol esters with gaseous sulfur trioxide, neutralization with bases and subsequent heating with phase separation and to their use as surfactants.
2. Description of Related Art
Sulfonation products based on unsaturated fatty acid glycerol esters have long been known. As long ago as 1834, Runge obtained sulfonated oils by the action of sulfuric acid on olive oil or castor oil. These oils are still in use today as auxiliaries, so-called "Turkey red oils", in the dyeing of textiles (H. Stache, H. Grossmann, "Waschmittel", Springer-Verlag, Berlin-Heidelberg, 1985). Other sulfonated oils are used in the wet finishing of textiles, in hand-washing pastes, as thickeners in paints, as hydrotropes for liquid detergents, corrosion inhibitors or emulsifiers for mineral oils (Soap. Cosm. Chem. Spec. (1975) 39).
The two patent applications PL 120 511 and SU 475 391 describe processes for reacting unsaturated triglycerides, for example from the oleic-acid-rich fraction of tall oil, with sulfuric acid. The addition of H.sub.2 SO.sub.4 onto the double bond of unsaturated fatty acid glycerol esters leads to the formation of sulfates which are characterized by --C--O--S-- bonds and hence are labile to the aggressive effect of acids. Accordingly, the use of products such as these is confined to the neutral to mildly alkaline range.
Alternatively, the sulfonation reaction also be carried out with oleum, i.e. with sulfur trioxide which is dissolved in sulfuric acid in a concentration of up to 65% by weight. Although, in addition to the formation of sulfates, this process leads mainly to the formation of sulfonates having an acid-stable --C--S-- bond, it is attended by the serious disadvantage that the sulfuric acid used as solvent has to be neutralized together with the sulfonic acids obtained so that the products are burdened by an undesirably high electrolyte content which is problematical in many applications.
German patent application DE 12 46 717 describes the sulfonation of unsaturated fatty acid glycerol esters with gaseous sulfur trioxide in admixture with an inert gas. However, since undesirably strong discoloration of the products is observed in addition to sulfonation with increasing reaction temperature and quantity of SO.sub.3 and can lead to carbonization in cases where the sulfonating agent is used in relatively large quantities, the process is confined in its application to temperatures in the range from 0 to 20.degree. C. and to ratios of fatty acid ester to sulfur trioxide of 1:0.5 to 1:1.7. Accordingly, it is only possible in this way to obtain sulfonation products of unsaturated fatty acid glycerol esters which have a low content of organically bound sulfur.
Finally, German patent application DE 34 37 443 Al describes a process for reacting both unsaturated fatty acid glycerol esters and saturated fatty acid esters with gaseous sulfur trioxide. However, the disadvantage of this process is that the production of homogeneous mixtures of both components involves considerable outlay on equipment, in addition to which the sulfonation products have a high percentage content of .alpha.-fatty acid methyl ester sulfonates.